The kinetics of the ATP hydrolysis by Na-K ATPase has been monitored with NIR spectroscopy. Previous results have determined that the relative amounts of ATP, ADP, and PO4 in equilibria solutions can be quantitatively determined with NIR spectroscopy. The major advantage of using NIR spectroscopy is the time-resolved capability of the method, allowing the spectroscopist to monitor reactions at very fast time scales. With this in mind, we have observed the hydrolysis of ATP with near infrared spectroscopy in the ten second time regime. Changes in the NIR spectral region reflect the enzymatic hydrolysis of ATP to ADP. Separation of these spectral changes to their separate components has not been accomplished; however, the overall change of optical density correlates linearly with independent assay of inorganic phosphate. With the advances in near infrared technology rapidly progressing, the extension of the temporal resolution as well as the separation of components is hoped to be achieved.